Sleep paralysis is a phenomenon where a person experiences temporary inability to move or speak upon waking or falling asleep. It is caused by a disassociation between the sleep and wake cycles where the mind awakens but the muscles remain paralyzed. Symptoms include vivid hallucinations of an intruder in the room and feelings of panic due to the temporary paralysis. Prevention methods include avoiding sleeping on one's back, managing stress, maintaining a regular sleep schedule, and in severe cases medication may help.